Restraining Capacity Increase To Achieve Ultrastable Lithium Storage: Case Study of a Manganese(II) Oxide/Graphene-Based Nanohybrid and Its Full-Cell Performance

As is well known, a gradual increase in capacity during cycling is a common phenomenon in previously reported oxide-based anodes for lithium-ion batteries. However, not only may this be superfluous for practical applications, but it may also imply the presence of some electrochemical instabilities and side reactions. To achieve ultrastable Li storage without such a gradual increase in capacity, the mechanism of this increase by using a MnO/graphene-based nanohybrid (MnO@C/RGO) as an example was comprehensively explored. Then, the gradual increase behavior of the specific capacity was effectively restrained by rationally optimizing the cutoff voltage, which resulted in the MnO@C/RGO electrode maintaining a nearly constant capacity during cycling at different current densities. Taking the high current density of 2Ag(-1) as an example, there was no clear capacity change (increase/attenuation) even over 2000cycles with stable coulombic efficiencies of around 99.7%. This ultrastable Li-storage capability should mainly benefit from rational testing parameters and an optimal 3D conductive network. More importantly and interestingly, full cells were also assembled and tested by coupling MnO@C/RGO and commercial LiFePO4 as the anode and cathode materials, respectively. The full cells impressively exhibited superior rate performance and excellent cycling stability.